Roasting sulphide ores



F. G.. BREYER ET All..

ROASTING. SULPHIDE ORES Filed Feb. v. 1922 2. sheets-sheet- 1 Aug., 7, i923.

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appliance anni February niaaa seria; no. esame.

To all whom z't may concern:

Be it known that We, FRANK' G. Beieren, JOHN P. HUBBELL, and DUNCAN M. Kumi, residing at Palmerton, county of Carbon, State of Pennsylvania, have invented certain new and useful Improvements in Roasting Sulphide Ures; and We do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which itappertains to make and use the same.

'llhis invention relates to the desulfurizing of zinciferous sulphide ores, and has for its object the provision of an improved method of desulfurizing such ores.

Zinciferous sulphide ores, as mined, contain, in addition to zinc sulphide or blende, varying amounts of other metalliferous sulphides, such as galeria7 pyrit/e, and the like, as Well as varying amounts of gangue constituents. rllhe raw ore, crushed to suitable size for the particular mode of ore dressing employed, is usually subjected to appropriate treatment, such as jigging, tabling, magnetic separation, dotation, etc., for eliminating to the desired extent the gangue constituents and, in some instances, one or more of the metalliferous constituents other than zinc sulphide. rlihe zinciferous sulphide concentrates resulting from such customary modes of ore dressing are in a nely divided condition varying, according to the particular mode of concentration emloyed, from one fourth inch mesh and ner, in the case of jig concentrates, to one one-hundredth inch mesh and ner, in the p case of flotation concentrates.

rllhe present invention contemplates an improved method of desulfurlzing or roastmg zinclferous sulphide ores or concentrates in a linely divided condition, that is. of one-Y fourth inch mesh and finer. Throughout this specification and the appended claims the ex ression zinciferous sul hide ores isk to Abe understood as including raw ores, concentrates, or other materials containing a relatively high percentage of zinc sulphide or blende. lin addition to zinc sulphide orv blende, the zinciferous sulphide ore, concentrate, or other material, may, and usually does, contain other metalliferous constituents snch as alena, pyri'te, etc., and it is to be understood that the method of the invenmetalliferous constituents, generally inirelatively smalll percentages, such as are ordinariiy present 1n zinciferous sulphide ore ,or concentrates. y

Zinclferous sulphide ores have heretofore.

been desulfurized or roasted by various processes and in various forms of apparatus such, for example, as shaft furnaces, reverberatory furnaces, Inutile furnaces, etc. The complete elimination of the sulfur from such ores, even if desirable, issubstantially impracticable under commercial operating conditions, and it is customary in the art to regard the ore as sufliciently roasted or desulfurized for any subsequent metallurgical treatment When its fault sulfur content is reducedtol3% and preferably .to less-than 2%, in which condition the ore is said to be dead-roasted or sweet-roasted'. As is Well understood in the art, the fault sulfur is the sulfur in the roasted or desulfurized product which might have been driven off under ideal roasting conditions. The partial desulfurization of zinciferous sulphide ores can be eected with little practical diiiculty and Without the application of external heating, but, as far aswe are aware, it has heretofore been the general practice in deadroasting zinciferoussulphide ores to effect the last stages of the desulfurization by the application of external heat, and We knowV of no method heretofore successfully used in practice for autogenously dead-roasting zinciferous sulphide ores.

l/Vhere the sulphide dioxide gases resulting from the desulfurization of thev ore are employed in the manufacture of sulfuric acid, it is difficult in the heretofore customary processes of desulfurization to maintain uniformity in the sulfur dioxide content of the resulting gases because such gases are richer in sulfur dioxide duringthe earlier stages of the desulfurization than during the latter stages, and more particularly because the raking of the ore charge is generally intermittent vand the gas is much richer of a gas of a substantially uniform' temperature and sulfur dioxide content. The present invention contemplates a method of desulfurization which is of special advantage in this respect.

. The desulfurlzation or roasting of zinciferous sulphide ores may be regarded as ideal or 100% eflicient from the acid as well as the washing standpoint where- 1. There is complete control of theamount of sulfur left in the calcine; l

2. No fuel is used but the ore itself;

3. A roasted ore is produced whose physical properties are satisfactory for further metallurgical treatment;

4. A s most desirable for acid manufacture 6-8% SO2) is produced;

While the ignition temperature of zinc sulphide is around 600 C., and consequently a temperature of over 600 C., in the roasting zone should theoretically be 'ample for effecting the desired desulfurization of the ore, we have found in practice that the most satisfactory desulfurizin temperature is between 860 C. and 1000 As is commonly understood in the art, the diiiiculty in roasting zinc blend lies in preventing the temperature from rising too h1gh in the earlier stages of the desulfurization, when the amount of fuel (sulfur) .in the ore is relatively high and desulfurization is most active, while at the same time maintaining in the ore suilicient heat to complete the desired desulfurization during the later stages thereof when the amount of fuel (sulfur) in the ore become so depleted as to furnish too little heat to maintain its own combustion, as well as maintaining, during the later stages of desulfurization, a sufficiently high temperature to prevent the formation of sulfates and to decompose those which may have formed.

Our improved method of desulfurizing zinciferous sulphide ores, when carried out in accordance with Our preferred practice, more closely approximates the aforementioned ideal conditions of desulfurization than any other method now known to us. In its preferred and Vcomplete aspect the method of thetinvention involves agglomerating finely divided zinciferous sulphide v ore into porous lumps of substantial size and subjecting the agglomerated ore to a regulated desulfurizing environment for effecting the desired elimination of sulfur from the ore with the production of a roasted or desulfurized product containing not over three per cent of fault sulfur and the production of a gaseous product of substantially uniform sulfur ldiofxide content of from about 5% to about 8%. The agglomeration of the ore may be effected by briquetting, by sintering, or by any other 'appropriate procedure adapted to roduce porous agglomerates ofthe finely divided ore. In

-fur1zing pass throu h the furnace carrying .out the invention, the agglomerated ore is caused to travel through an appropriate desulfurizing environment which is maintained by passing through the agglomerated ore, preferably 1n a direction opposite to the direction of travel of the ore, a combustion supporting gas (such as air) at least a portion of which is preheated, preferably in part at least by the hot roductsresulting from the desulfurization.

he combustion supporting gas is preferably introduced into the agglomerated ore at two, or more, different stages inthe -desulfurization, the portion of the combustion supporting gas introduced into the ore at a later stage in the desulfurization being at a considerably higher temperature than 'the portion of the combustion supporting gas introduced into the ore at an earlier stage in the desulfurization.

The desulfurizatiou ofthe agglomerated ore may advantageously-be carried out in a well insulated shaft furnace, prefs. ably of tapered section (larger at the bottom than at the top), and provided with two or more sets of tuyres appropriatelydistributed at dierent levels between the top and bottomI of the furnace. Air (or other appropriate combustion supporting gas) preheated to a temperature preferably' around 650. C., and generally in amount from about one-third to two-thirds of the total air required for the desulfurizing operation, is introduced into the furnace through the lower set or sets of tuyres, and cold air (at or .about atmospheric temperature), and generally in amount from about two-thirds to one-third of the total air required for the desulfurizing operation, is introduced through the upper set or sets of tuyres. The porous lumps. of agglomerated ore and the air for desulcounter-current direction, in the course of which the. air passes upwardly through the agglomerated ore, and the agglomerated lumps of' ore pass progressively downward through the. shaft furnace, whereby the freshly charged ore while rich in fuel value, is subjected to the combined preheated and cold air introduced into the furnace through all of the sets of tuyres, and later, when more or less depleted of fuel value, the agglomerated ore is subjected only to preheated air introduced into"the furnace through the lower set or sets of tuyres. The exi-t gases resulting from the desulfurizing operation are withdrawn from near the top of the furnace and the heat thereof is employed for preheating the air supplied to the lower set or sets of tuyres.

The exit gases from the desulfurizing operation have a very uniform sulfur dioxide content of from 5 to 8%, which is a marked improvement over the heretofore customary processes of roasting zinciferous sulphide in y I vantageously utilized in the manufacture incassa f ores, the exit gases in `these prior processes having a very non-uniform sulfurl dioxide content varying on the same furnace from as low as 1% to as high as 7%.but-averaging about 3fl%. The exit gases produced in the practice of the invention, after giving up a certain amount of their heat in preheating the air introduced into the desulfurizing furnace through the lower set or sets of tuyres as aforementioned, are adof sulfuric acid.

While it is our present preferred practice to carry out the method of the invention in a shaft furnace, we wish it to be understood that the desulfurizing .process of the invention may be carried out in other types of furnace, such, for example, as straight line furnaces with traveling hearths (or cars or wagons) or in rotary hearth or in rotary kiln types of furnaces. For the purposes of explanation, we will proceed to a more detailed description of the practice of the invention as carried out in a shaft furnace ofthe type and construction illustrated in the accompanying drawings in which Figures 1 and 2 are elevations, partly in section, of two furnace structures and their appurtenances which we have found admirably adapted for the practice of the invention.

ln the practice of theinvention as hereinafter particularly described, .the finely divided zinciferous ore is agglomer'ated by briquetting, but we wish it to lbe understood that the process of the invention is not limited to the treatment of ore in the form of briquettes but, on the contrary, contemn plates the desulfurization of finely divided zinciferous sulphide ore artificially -agglomerated in other ways, such, for eX- ample, as by sinteringthe finely divided ore, with subsequent crushing, if necessary, of the sinte'red product to lumps of suitable size for desulfurization in accordance with the invention. The briquetted, or otherwise artificially 'agglomerated, material should possess sufficient mechanical strength to withstand without crumbling or breaking the handling incident to storage, conveying to the furnace and to charging into the furnace either by hand or otherwise. Moreover, it is desirable that the agglomerated material possess such resistance to crumbling or breaking as to enable the briquettes or other agglomerates to substantially maintain their original form during the entire furnacing operation, so that they are, for the greater part, discharged from the furnace in substantially their original hysical form, yand without .the formation o an ob-l jection-able amount of lines. n

-We .have secured excellentl results in briquetting finely divided zinciferous sulphide ore in the following manner. The

finely divided ore together with a suitableA binder (preferably lconcentrated waste sulfite liquor of the sullite paper pulp industry) isplaced in a revolving mixer of the kind employed for the mixin of concrete,

. and therein mixed 4until the binder is thoroughly incorporated throughout the ore mass. From 3% to 5% (on the weightf of the ore) of the'concentrated waste sulte liquor of 30%Baume is a satisfactory amount to employ for binding purposes.

F rom the aforementioned mixer, our cusvantage consists of cooperating rolls pro` vided with cooperating molding pockets so that when the material is fed into`the pans of the rolls froml above it is molded into briquettes of predetermined shape and dimensions. The two rolls of the briquetting press are held together by heavy spring pressure so yas to exert la compressive force upon the material, as fit is being formed into the briquettes, of about 2000 pounds to the square inch. The briquettes are next dried at a temperature of approximately 200 C. for aperiod of from l to 2 hours. rllhe dried briquettes are then cooled and stored under cover for subsequent use.

The size of the briquettes bear a denite relationship to the size of the furnace and the speed with which the charge passes through :the furnace. Where the ore is to 'be dead or sweet roasted, the size of the briquette should be so proportioned'with respect to the size of the furnace and the speed with which the charge passes therethrough that the desulfurization penetrates uniformly to the'center of the briquette leaving no unroasted portion or core within the briquettes. With a shaft furnace aboutlt feet in height having a tapered roasting chamber ofcircular section about 2g feet in diameter at the bottom and about 1% feet in diameter. at the top, wev have secured eX- cellent results with briquettes weighing approximately 2 to 3 ounces, the briquettes passing through the furnace in about 24: hours. With larger furnaces, or with slower progress of the vcharge throughout the furnace, larger briquettes may be used, and we have successfully dead roasted by the process of the invention briquettes weighing ap-` proximately 5 to 6 ounces.

Referring now to F ig. 1 of the accomf panying drawings, there is diagrammatically represented a shaft furnace construct-` ed for the most part of fire brick 5 surrounded by a comparatively thick layer 6 of heat insulating material, such, for ex ample, as sil-o-cel.

is supported on concrete pillars 7 and I- y The furnace structure beams 8.

The shaft furnace is provided with three sets of tuyres 9, 10 and 11 arranged to introduce air or other appropriate combustion supporting gas into the roasting chamber at three different levels. The two upper sets of tuyres 9 and 10 are directly connected to the air main 13 and serve to 1ntroduce air at atmospheric temperature, or thereabouts, into the roasting chamber at two different levels. The 'relative amount of cold air introduced into the roasting chamber through the tuyeres 9 and 10 can he regulated by thevalvesv 14.

rlhe lower tuyres 11 are connected to the air main 13 through a Well insulated prelieater 15. The air circuit of this preheater comprises a pair of spaced headers 16 connected by a plurality of vertical pipes 17, and a pipe`18 communicating with the upper header 16 and passing into the conduit 19 for the exit gases of the desulfurizing operation. From the conduit 19 the hot air pipe 18 passes to the tuyre's 11 and. is thoroughly insulated by a relatively thick packing of heat insulating material 20. A pair of horizontally disposed and spaced baffles are preferably arranged lin the preheater to keep the top part of the chamber as hot as possible by preventing radiation downward. i

In practicing the method of the invention in the apparatus illustrated in Fig. 1 0f the drawings, the agglomerated ore is fed into the shaft furnace through the top. The top of the furnace is normally closed by a thick tile 21 and a sand-sealed cover 22. Under normal operatinor conditions the shaft furnace is entirely filled with the agglomerated ore, the sulfur content o f the ore varying from a maximum to a minimum from the top of the furnace toward the bottom. Hot air, preheated to a temperature of from about 400"-800o C., is introduced into the agglomerated ore through the lower set of tuyres 11. In practice, we find that from about one-third to about twothirds of the total air required for the desulfurizing operation should be 'preheated and introduced into the agglomerated ore through the lower set or sets of tuyres. Cold air, thatl is at or about atmospheric temperature, is introduced into the agglomerated ore through either or both of the upper sets of tuyres 9 and 10.

`Pyrometers 23, preferably of the thermocouple type, are appropriately disposed to indicate the temperature at various levels within the shaft furnace. We prefer to arrange these pyrometers in proximity to each of the sets of tuyres, and also to arrange one pyrometer in proximity to the Outlet flue 2t for the exit gases. In Figure tures within the shaft furnace at which they are respectively located. Preferably, the indications of the pyrometers are recorded on a time-actuated record sheet iii order to facilitate the proper control of the desulfurizing operation from the pyrometric indications.

n carrying out the invention a regulated des'ulfurizing environment is maintained withinthe shaft furnace by appropriately regulating the relative amounts of air introduced into the furnace through the three sets of tuyres 9, 10 and 11.- From the readings of the pyrometers 23, the relative amounts of air introduced into the agglomerated ore in its progressive travel through the shaft furnace are so controlled and regulated as to maintain the temperature of the agglomerated ore during the desulfurizingv operation above 760 C., the aim being in this control and regulation to maintain the agglomerated orev throughout the entire desulfurizing operation as nearly as possible at the optimum temperature of from .800 C. to 10000 rllhe roasted or desulfurized product is withdrawn from the bottom of the shaft furnace through doors 2 5. lt will, of course, be understood that the charging and discharging of the furnace may be carried out in a continuous manner, rather than intermittently as represented by the furnace construction of Fig. 1. The hot gaseous products from the desulfurization pass from the furnace through the outlet flue 24 and conduit 19 into the preheater 15 where they come in intimate contact with the elements l1t, 17 and 18 of the air circuit of the preheater. From the preheater the gaseous products pass through a flue 26 and may advantageously be utilized in the manufacture of sulfuric acid.

A slightly modified arrangement `of apparatus for practicing the method of the invention is diagrammatically indicated in Fig. 2 of the drawings. Similar elements in the apparatus of Figs. 1 and 2 are indicated by the same reference characters. The apparatus of Fig. 2 is provided with an additional hot air tuyre 12 on substantially the same level as the tuy`eres 11 but centrally disposed within the interior of the shaft furnace. The furnace itself is constructed to enable the withdrawal from the bottom thereof of the desulfurized or roasted ore along the central axis, and to this end a center discharge well 26 communicates with the bottom of the shaft furnace and is provided at its lower end with a door 27 for withdrawal of the desulfurized 0r6 from the bottom ofthe well,

ifi-ease? An auxiliary preheating furnace or booster 28 is provided in the apparatus of Fig. 2 for assisting in preheating the air to the desired temperature for the proper control ofthe desulfurizing operation. The booster 28 may conveniently' consist of a coal-tired preheating furnace in which the coils 29 of the hot air circuit are exposed to the heat of the hot products of combustion t@ of the hre. Hot air may be introduced into the shaft furnace through either or both of the lower tuyeres l1 and l2 by appropriate adjustment of their respective valves 14, and

cold air may similarly be introduced into the shaft furnace through either or both of the upper sets of tuyeres 9 and 10.

The practice of the improved method of desulfurization ofthe invention in the apparatus illustrated in Figs 1 and 2 of the 2U, accompanying drawings is comparatively simple consisting, 'for the most part, of

adding briquettes, or other appropriately agglomerated material, to the top of the furnace, removing the roasted orl desulfurized briquettes from the bottom of the furnace and introducing air near the bottom and along the sides of lthe furnace in the proper proportions to maintain the desired aforementioned conditions of desulfurization. 'llhe Contact between the air and the ore is excellent, and, due to the porosity of the briquetted or otherwise agglomerated material, the air is readily distributed throu h the entire mass of ore undergoing desul urization. The nature of the shaft furnace isv such that there can be no dead air spaces, and furthermore there is no dillution of unroasted ore with roasted ore as the roast nears completion.

The method of the invention is particularlyvadapted for the dead or sweet roastin of zinciferous materials, so that the roaste or desulfurized material is adapted to be utilized, without further treatment, in the manufacture of zinc ozide by the Wetherill process, or in the manufacture of spelter in' thecustomary lzinc distillation furnaces, or for any other purpose where roasted zinc A sulphide ores are usable. Where the roasted @n product is to be employed in the manufacture of substantially lead-free zinc products,

the roasting should be carried on until the .i fault sulfur inthe charge is less than 3 per cent, and preferably not over 2 per cent. lin roasting leaded zinciferous sulphide ores, wherethe roasted product is' to be employed in the manufacture of leaded zinc products, such as leaded Zinc oxide, the fault sulfur Vin the roasted product may be as high as 10 per cent, and in practice is frequently around 8 to 7 per cent. ln vany case, in accordance with the present invention, the appropriately agglomerated zinciferous ore in the form of lumps of substantial size, is roasted to effeetsuch desulfurigation of the sulphides as is required in the subse uent metallurgical treatment of the roaste material.

l. The process of desulfurizing nely divided zinciferous sulphide ores which coinprises agglomerating the hnely divided ore into lumps of substantial size, causing the agglomerated ore to progressively travel through a desulfurizing environment, and maintaining said desulfuriaing environment by passing through the agglomerated ore a y by passing through the agglomerated ore acombustion supporting gas at least a portion of which is preheated by the hot gaseous products resulting from the desuifurizatiou.

3. 'lhe process of desulfurizing nely f divided Zinciferous sulphide ore which comprises agglomerating the hnely divided ore into lumps of substantial site, causing the agglomerated ore to progressively travel through a desulfurizing environment under regulated desulfurizing conditions for ed'ecting a gradual elimination of sulfur from the ore, and maintaining the aforementioned re lated desulfurizing conditions by passing t rough the agglomerated ore in a direction opposite to the direction of travel of the ore a combustion supporting gas at least va portion of which is preheated in part at least by the hot gaseous products resulting from the desulfurization.

4s. The process of desulfurizin finely divided zinciferous sulphide ore which comprises agglomerating the finely divided ore into lumps of substantial size, causing the agglomerated ore to travel through a desulfurizing environment under regulated desulfurizinof conditions for eecting the desired elimination of sulfur from the ore, and maintaining the aforementioned re lated desulfurizing conditions by passing t rough the agglomerated ore a combustion supporting gas at least a portion of which is'preheated in part at least by the hot products resulting from the desulfurization.

5. The process of desulfurizin finely divided zinciferous sul hide ore which comprises agglomerating t e tinely divided ore into lumps of substantial size, causing the agglomerated ore to'travel through a desulfurizing environment under regulated desulfurizing conditions for e'ecting a gradual elimination of sulfur from the ore and the production of a desulfurized product containing not over' three per cent of fault sulfur, and maintaining the aforementioned ne Q regulated dsulfurizing conditions bypassing through the agglomerated ore a combustion supporting gas at least a. portion of which 1s preheated in part at least by the hot gaseous products 'resulting from the desulfurization.

6. The process of desulfurizing finely divided zinciferous sulphide one which comprises aggloinerating the finely divlded ore into lumps of substantial size,.caus1ng the agglomerated ore to progressively travel through a desulfurizing environment under regulated desulfurizing conditions for effecting the desired e imination of sulfur from the ore and the production of a desulfurized product suitable for subsequent metallurgical treatment, and maintaining the aforementioned regulated desulfurizing conditions by passing t rough the agglomerated ore a combustion supporting gas at least a portion of which is preheated in part at least by the hot gaseous products resultin from the desulfurization.

g. The process of desulfurizing finely divided zinciferous sulphide ore which comprises agglomerating the finely divided ore into lumps of substantial size, causing the agglomerated ore to travel through a esul- :turizing environment under regulated desulfurizing conditions for eil'ecting a gradual elimination of sulfur from the ore and the production of a seous product having a substantially uni orni sulfur dioxide content of from about 5 to about 8. per cent and maintaining the aforementioned regulated desulfurizing conditions by passing through the agglomerated ore a combustion supporting gas at least a portion of which is preheated. i

8. The process .of desulfurizing finely divided zinciferous sulphide ore which comprises agglomerating the finely ,divided ore into lumps of substantial size, causing the agglomerated ore to progressively travel through a desulfurizing environment under regulated desulfurizin conditions for eifecting a gradual elimination of sulfur from the ore andthe reduction of a desulfurized product containing not over three per cent of fault sulfur, and maintaining the aforementioned regulated desulfurizing conditions by passing through the agglomerated ore in a direction approximately opposite to the direction of travel of the ore a coinbustion supporting gas at least a portion of which is preheated in part at least by the hot gaseous products resulting from the dev sulurization.

9. The process of desulfurizing finely divided zinciferous sulphide ore which comprises agglomerating the finely divided ore lnto lumps of substantial size, causin the ore to progressively travel through a esulfurizing environment under regulated desulfurizing conditions,' maintaining the aforementioned-regulated desulfurizing conditions by paing 'throu h the ore a. combustion supporting gas w ich is introduced into the ore at two or more diierent stages in its desulurization, the portion of the combustion supporting gas introduced into the ore at a later stage in the desulfuriza- A through a desulfurizing environment, maintaining said desulfurizing environment by passing through the agglomerated ore a comustion supporting s at least a portion of which is preheated,a and preheating said combustion supporting gas solely by heat derived from hot products resulting from the desulfurization.

il. rl'he process of desulfurizing finely dividedzincierous sulphide one which comprises agglomerating the finely divided ore into lumps of substantial size, causing the agglomerated ore to progressively travel through a desulurizing environment under regulated desulfurizing condi-tions for-effecting a gradual elimination of sulfur from the ore and the production of a aseous roduct having a substantially uni orm su fur dioxide content of from about 5 to about 8 per cent, maintaining said regulated des'ulfurizing conditions by passing through the agglomerated ore a combustion lsupporting gas at least a portion of which is preheated, and preheatingsaid combustion supporting gas solely by heat derived from hot products resultin from lthe desulurization.

12. T e process of desulfurizin finely divided zinciferous sul hide one which coinprises agglomerating title finely divided ore into lumps of substantial size, causing the agglomerated ore to progressively travel through a desulfurizing environment under regulated desulfurizing conditions for effecting a gradual elimination of sulfur from the ore and 'the production of a desulfurized product containing not over three per cent of fault sulfur, maintaining said regulated desulfurizing condition by assing through the agglomerated ore a com ustion supporting gas at least a portion of which is preheated, and pneheating said combustion supporting gas solely by heat derived from hot products resulting from the desulurization.

13. The process of desulfurizing finely divided zinciferous sulphide ore Which` comprises agglomerating the 'finely divided ore into lumps of substantial size, causing the agglomerated ore to -progressively travel through a desulfurizing environment under nauseas regula-ted desuliurizing conditions tor etfooting a gradual elimination of sulfur trom the ore and the production of a desulfurized product containing not over three per cent of :fault sulfur and the production ot a gaseous i roduct having a substantially uni- :torni su fur dioxide content ot jfrom ab'out 5 to about 8 per cent, maintaining said regulated desuliurizing conditions by passing through the agglomerati/ed ore a combustion supporting gas at least a portion ot which is preheateda and preheating said gas solely by heat derived from hot products resulting from the desuli'urization.

14. The process of desulturizing nely divided zinciferous sulphide ore which comprises agglomerating the finely divided ore into lumps of substantial size, causing the agglomerated ore to progressively travel through a desulfurizing environment under regulated desulfurizing conditions tor edecting a gradual elimination of sulfur 'from the ore and the production ot a desulturized product containing not over three per cent of fault sulfur and the production ot a gaseous product having a substantially uniform sulfur dioxide content of from about 5 to about 8 per cent and maintaining the aforementioned regulated desulturizing conditions by passing through the agglomerated ore a combustion supporting gas at least a portion of which is preheated.

` 15. rlhe proc/ess of desulturizing finely divided zinciferous sulphide ore which comprises agglomerating the nely divided ore into lumps of substantial size, causing the agglomerated ore to progressively travel through a desulturizing environment under regulated desulfurizing conditions for eccting a gradual elimination of sulfur from the ore and the production of a gaseous product having a substantially uniform sulfur dioxide content ot from about 5 to about 8 per cent and maintaining' the aforementioned regulated desulturizing conditions by passing through the ore a combustion supporting gas which is introduced into the ore at two or more diderent stages in lits desulturization7 the portion of the combustion supporting gas introduced into the oreI at a later stage in the desulurization being at a considerably higher temperature than a portion of the combustion supporting gas introduced into the ore at an earlier stage in the desulfurization.

16. The Iprocess of desulfurizin nely divided zinciferous sulphide ore Whlch comprises agglomerating the finely divided ore into lumps of substantial size7 causing the agglomerated ore to progressively travel through a desulfurizing environment under regulated desulfurizin conditions for effect- -ing a gradual elimination of sulfur from the ore and the production .fof a desulfurized product containing not over 3 per cent of fault sulfur, and maintaining the autorernentioned regulated desulfurizing tondin tions by passing through the ore a combustion supporting which is introduced into ore at tvvo or more different stages in its desuliuriaation, the portion ot the courbustion supporting gas introduced into the ore at a later stage in the desuliurization being at a considerably higher temperature than portion ot the combustion supporting gas introduced into the ore at an earlier stage in l the dnlturisation.

rz. 'ria prima or aanneming suny in! 'aforementioned regulated desuliurizing conditions by passing through the ore a combustion supporting gas which is introduced into the ore at tvvo or more di'erent stages in its desuliurization, the portion of the cornbustion-supporting gas introduced into the ore at later stage in the desulturization being at a considerably higher temperature than a portion of the combustion supporting gas introduced into the ore at an earlier stage in the desulturization.

18. 'lhe process of desulturizin iinely divided zinciferous sulphide ore vv ich comprises agglomerating the nely divided ore into lumps ot substantial size, causing the agglomerated ore to progressively travel through a desulturizing environment under regulated desulturizing conditions for eiftecting the gradual elimination ot sulfur from the ore and the production ot a ioaseous product having a substantially uni oran sulfur dioxide content ot from about 5 to about 8 per cent, maintaining the aforementioned regulated desulfurizing conditions by passing through the ore a combustion supporting gas which is introduced into the ore at two or more diderent stages in its desulfurization,v the portion of the combustion supporting gas introduced into the ore at a later stage in the desulfurization being at a considerably higher temperature than a portion of the combustion supporting gas introduced into the ore at an earlier stage in the desulfurization, and preheating the portion of the combustion supporting gas of higher temperature in part at least by the hot aseous products resulting :trom the desul rization.

19. 'The process of desulturi'zing nely divided Azi1icife1 ous"sulphideore which comprises agglomerating the 'finely divided ore 'intoi-luinpsofsubstantial size, causingthe agglomerated ore Ato progressively travel -5 wthrougha desulfur'izin'g environment 'under .regulated 1 de'sulfurizing conditions. for-.effectingfa 'gradual elimination lof sulfurv fromthe ore-and the production of a desulfurizeclA Y. roduct containing not -over 35 per eent of. :10l aultrsulfur, maintaining the aforementioned 7 regulated desulfurizing conditionsby pass-` ing through theore a. combustion supporting -g`a `s -which. isintroduced into1 the ore at vtwo different stages in. its desulfuriza- 1 5 g tion, the-portion oflfthe conibustion supportl ing gas introduced intotheore at a later stage inthe desulfurization being at a considerably higher temperature than aportion l ofthe combustion--supportingl gas introduced 2Q. into-the'zore 'at an earlier stage-in thejdesulfu'rization, and -p reheating the portion of the combustion 'supporting gas of' `higher temperature Vin part atleast by thehot asf -eous productsresulting from the desul uri- 25. ization; 1

A The .process of desulf'urizing"v finely divided zin'ciferous sulphide ore .which cornprises agglomerating-the finely divided ore. 1ritolum`ps of substantial sizeycausing the Iaggloinerated ore toA progressively travel lthrough a desulfurizing environment under 'regulated desulfurizing conditions' foreiecting a' V adual .elimination of `sulfur" from the ore an the p'roauctlon ot' a desulfrized product containing not overv 3 per cent'of fault sulfur andthe production of a-gase'ous product having a substantially uniform sulfur dioxide content of-,from about-5 to -aboutSvper cent maintaining the aforementioned regu: 40

lated de'sulfurizing conditions by passmg through the crea combustion supporting' gas which is introduced into the ore in two-or more'diil'erent stages in its desulfurization, ya portion ofthe combustion supporting gas.

introduced into the lore at a later stage in the desulfurization bein at a considerably highertemperaturet an a portion of the tures.

FRANK G. BR-EYER.

JOHN P. HUBBELL. DUNCAN M. KEER. 

